The present invention relates to the cooling of heated plates, and more particularly to the cooling thereof by means of a cooling slot passing therethrough.
The invention herein described was made in the course of or under a contract, or a subcontract thereunder, with the United States Department of the Air Force.
The cooling of heated plates in various machinery types has been performed by a multiplicity of methods. One such method is the passing of a cooling fluid through a cooling slot within the plate. It has been found that the convective heat transfer of this type cooling is improved in efficiency by promoting turbulence within the cooling slots.
Heated plate cooling concepts have found particular application in the gas turbine engine art wherein it is often desired to partially cool airfoil blades (of the compressor or turbine blade variety) by passing cooling fluid from an internal cavity within the blade through a cooling slot located in the trailing edge of the airfoil blade. In the past, the trailing edge slot has been provided with a number of protuberances or nodes which extend from the walls of the slot into the slot and engage the cooling fluid passing therethrough. These nodes serve the dual function of promoting turbulent fluid flow through the slot and additionally of increasing the surface area of the trailing edge presented to the cooling fluid. These two functions combine to substantially improve the efficiency of heat transfer from the trailing edge of the cooling fluid.
The fabrication of airfoil blades incorporating such a noded trailing edge slot has been a particular problem in the prior art, which has relied upon either casting or sheet metal fabrication techniques. Casting has limitations due to the relatively difficult coring and brazing problems involved. Sheet metal fabrication has proven difficult due to the requirement that the braze alloy melt at temperatures considerably lower than the melting point of the parent material. These latter characteristics are particularly unsuitable for use in gas turbine engines operating at elevated temperatures.
The present invention provides solution to the fabrication problems of the prior art by permitting the installation of turbulence promoting nodes within slots and trailing edges (and similarly in other heated plate applications) which result neither from casting nor sheet metal fabrications, by means of the formation of intersecting passages through the trailing edge by conventional means such as crossdrilling.